A total of 32 members of Congress signed the letter to Attorney General Jeff Sessions. In addition to Rep. Ken Buck, the letter was signed by two other Colorado congressmen: Republicans Reps. Mike Coffman and Scott Tipton.

U.S. Rep. Ken Buck asked Attorney General Jeff Sessions in a letter Monday to examine irregularities in the U.S. aluminum market that, officials said, may have raised the price of the product.

The letter, signed by 31 other members of Congress, also asked Sessions to determine whether antitrust violations have occurred in the market. Officials with Buck's office said in a news release the letter stems from concerns that S&P Global Platts, the rating service in charge of setting the price for the end product, has potentially started setting an artificial price for aluminum in cooperation with aluminum producers, merchants, traders and banks.

According to the release, end users of aluminum pay a price for the product that is partially set by the Midwest Transactional Premium, which factors in storage and transportation costs of the final product. The concern, officials said, is that Platts "has deviated from its standard practice of using spot transactions to set the price and is instead working with a few producers, merchants, traders and banks to set a potentially artificial price."

In the letter, the members of Congress said people who buy products such as soft drinks and beer are encountering pricing irregularities and "potential anti-competitive conduct."

"When monopolies manipulate aluminum prices, normal Americans suffer from higher prices for the products they buy," Buck, a Windsor Republican, said in the news release. "I encourage the attorney general to ensure a fair and transparent process for the pricing of aluminum in this country."

Officials also said since President Donald Trump's administration announced a 10 percent tariff on imported aluminum, the premium has undergone sharp price increases from November 28 to March. The premium, according to the letter, doubled to more than 20 cents per pound.

Recommended Stories For You

Colorado Republicans Reps. Mike Coffman and Scott Tipton also signed the letter.

— Sara Knuth covers government for The Tribune. You can reach her at (970) 392-4412, sknuth@greeleytribune.com or on Twitter @SaraKnuth.

Signatures collected

A total of 32 members of Congress signed the letter to Attorney General Jeff Sessions. In addition to Rep. Ken Buck, the letter was signed by two other Colorado congressmen: Republicans Reps. Mike Coffman and Scott Tipton.